1 phút = 60s

- Chu kì: T = \(\dfrac{t}{n}\)= \(\dfrac{60}{4}\)= 15 (s)

- Tần số: f = \(\dfrac{1}{T}\)=\(\dfrac{1}{15}\)(Hz)

- Tốc độ góc: T = \(\dfrac{2\pi}{\omega}\) \(\Rightarrow\) \(\omega=\dfrac{2\pi}{T}\)\(=\) \(\dfrac{2\pi}{15}=\dfrac{2}{15}\pi\) (rad/s)

- Tốc độ dài: \(\upsilon=r\omega\) ⇔ \(\upsilon=\dfrac{3}{2}.\dfrac{2}{15}\pi\) = \(\dfrac{1}{5}\pi\) (m/s)

- Gia tốc hướng tâm: \(a_{ht}=r.\omega^2\Leftrightarrow a_{ht}=\dfrac{3}{2}.\left(\dfrac{2}{15}\pi\right)^2\)\(\simeq\) 0,263 (m/\(s^2\))

I. Odd one out: 

1) C. homework

2) D. vacation

3) C. egg

4) B. work

5) A. city 

II. 6) D. the longest

7) D. mechanic

8) C. interesting

9) A. hard

10) B. fewer

(-26) + 148 + (-74) + (-86) + (-48)

= (-26 - 74 - 48) + 148 - 86

= -148 + 148 - 86

= 0 - 86

= - 86

3. A calorie is energy that helps us do our everyday activities.

4. I volunteer because it makes a difference in our community.

Task 2: 

1. Yes, I have. I have done some volunteer work such as donating food and clothes.

2. To help people in a flooded area, I can donate food, clothes, and money.

(-26) + 148 + (-74) + (-86) + (-48) = -86

D

1. The man whom you met at the party last night is a famous doctor.

2. That man, whom you lent money last week, has gone.

3. The girl who chatted with him yesterday arrived here at 6:30.

4. The policeman who caught the criminal received a reward.

5.  I’m reading a book which/that I bought in Sydney in 1996.

1. The old castle has been transformed and it is now a luxury hotel.

2. We are good friends. We have known each other for a long time.

3. I left my bicycle here and now it’s gone. My bicycle has been stolen.

4. They have finished their assignment.

5. The sick child has been examined by the doctor.

6. The bridge has been built since last year. 

7. They have lived in London for over ten years.

8. She speaks English fluently. She has learned English since she was 

1. The old castle has been transformed and it is now a luxury hotel.

2. We are good friends. We have known each other for a long time.

3. I left my bicycle here and now it’s gone. My bicycle has been stolen.

4. They have finished their assignment.

5. The sick child has been examined by the doctor.

6. The bridge has been built since last year. 

7. They have lived in London for over ten years.

8. She speaks English fluently. She has learned English since she was 

\(\dfrac{7}{18}\) là phân số nhỏ nhất